1. Field of the Invention
The present invention relates to an ignition timing control apparatus for controlling the ignition timing of a spark plug for an internal combustion engine mounted on a motor vehicle.
2. Description of the Related Art
An ignition timing control apparatus for an internal combustion engine functions to set a proper ignition timing for the internal combustion engine. An electric spark is generated by a spark plug in accordance with the operating condition of the engine. For instance, the ignition timing may be advanced when the engine is accelerating to increase the speed of the engine.
However, even when the engine is accelerating, especially during transient operation, e.g., sudden acceleration, where engine parameters for the speed of the engine vary in a short time, no substantial response to the ignition timing control is obtained. This may result in improper operation of the engine, e.g, knocking of the engine.
In Japanese Unexamined Patent Publication No. Hei 1-232169, an ignition timing control apparatus retards the ignition timing during sudden acceleration when the amount of variation of the throttle valve opening of the internal combustion engine exceeds a specific value. This mitigates the knocking caused by a change in engine output during sudden acceleration.
In the prior art ignition timing control apparatus; however, the ignition timing, if retarded in accordance with the amount of change in the opening of the throttle valve, will be retarded after the occurrence of knocking resulting from actual throttle valve operation. This also occurs in devices which retards the ignition timing when knocking is detected by a knocking sensor provided in the engine. The related art devices, therefore, cannot prevent the occurrence of the knocking before it happens, but only stops it once it occurs.